MOS transistors, with aluminum oxide as gate insulator, have been fabricated. The Al2O3films were formed by first depositing aluminum on freshly cleaned 10 &OHgr;‐cm silicon and then anodizing the aluminum in an oxygen plasma. All other steps used standard silicon technology. Electron diffraction showed that the insulator films are amorphous. The index of refraction is between 1.67 and 1.70 and the relative dielectric constant is 7.6. The devices have a threshold voltage of between ±0.5 V, and an interface state density of about 2 × 1010states/cm2‐eV. No evidence for ionic motion under positive bias was found at elevated temperatures. Under 1 MeV electron bombardment at various fluence levels and bombardment biases these devices showed excellent radiation resistance. Their radiation behavior is better than that observed for MNS or ``hardened SiO2'' devices.